Project Summary. Since HIV and HCV share common risk factors for infection, co-infections with HIV and HCV are frequently found in Injection drug users (IDUs). These two pathogens are also likely to be responsible for the highest infectious disease morbidity and mortality rates among IDUs. IDUs are the single largest risk group for HCV infection in the United States. However, we know little about direct opioids-virus (HIV and/or HCV) as well as virus-virus (HIV-HCV) interactions, which is a major barrier to a fundamental understanding of the immunopathogenesis of HCV disease and HCV-related morbidity in HIV/HCV- coinfected IDUs. A major barrier to address this key issue in vitro is the lack of a HCV infectious cell model system. Recently, three independent research groups have reported the development of a robust HCV infectious system in vitro. This newly established cell model provides an excellent opportunity for this proposed project. We have generated infectious HCV from this cell model in our laboratory. The goal of this study is to address our overarching hypothesis that the interactions between opioids (e.g., morphine), HIV, and HCV are a key determinant of the outcome of HCV/HCV infection. We will address previously un- recognized mechanisms by which morphine and/or HIV/HCV compromise the host cell innate immunity, leading to the persistence of viral infection and replication. Specifically, we will investigate the effects of morphine and the HIV proteins (Tat and gp120) on HCV infection, intracellular innate immunity, and the anti- HCV effects of IFN-a/Ribavirin in the human hepatic cells. We will utilize innovative cocultures of human hepatic cells with Kupffer cells to study the interactions of HIV with HCV in the presence or absence of morphine. Since Kupffer cells are the resident macrophages of liver, and are the target for HIV infections, the inclusion of Kupffer cells in this study is highly significant. Data arising from this study will be critical for a better understanding of opioids as a cofactor in the immunopathogenesis of HIV/HCV infection. The long term goal of this proposal is to develop host innate immunity-based treatment and prevention strategies for HIV/HCV-infected opioid abusers. Relevance to Public Health. There is little direct evidence available about the interactions between morphine, HIV and HCV in different cell systems, which is a major barrier to a fundamental understanding of HCV-related morbidity and mortality in HIV/HCV-infected IDUs. This research will contribute not only to our basic understanding of host cell innate immunity against HIV/HCV, but also to the design and development of innate immunity-based treatment and prevention strategies for HIV/HCV-infected opioid abusers.